1. Field
The present disclosure relates to a broadcast receiving apparatus including a display unit, such as a liquid crystal display (LCD).
2. Description of the Related Art
In a display unit composed of a large LCD provided in a frequency modulation (FM) receiver, noises caused by a drive signal for the LCD may be mixed into output sounds such that it is necessary to take measures against the mixing of the noises into the output sounds. For example, in a case in which the dot clock (pixel clock) corresponding to each pixel composing the LCD is equal to 37.125 MHz and a horizontal synchronous frequency is equal to 35.156 kHz, beat components within an audible range of a listener of the FM receiver occur and make annoying noises for the listener when harmonic components that are integral multiples of the horizontal synchronous frequency approach a reception frequency of FM broadcast waves.
Technology in a related art avoids the disadvantage caused by the approach of such a specific communication frequency (reception frequency) to the harmonic components of the operating frequency of the LCD. For example, an electronic device is known in which multiple dot clock frequencies for driving the LCD are prepared, and a dot clock frequency is selected so that the communication frequency band to be used does not interfere with (does not approach) the harmonic components of the dot clock frequency (see Japanese Unexamined Patent Application Publication No. 2010-141538).
In this electronic device, two types of radio communication having different communication frequencies are available. When the harmonic components of the dot clock frequency (for example, 68.35 MHz) for driving the LCD are within a certain range around the communication frequency (for example, 1,575.42 MHz) of one type of radio communication, the dot clock frequency is switched to a different frequency (for example, 68.90 MHz) to prevent the harmonic components of the dot clock frequency from approaching the communication frequency of the radio communication.
Although the dot clock frequency is switched to prevent the harmonic components of the dot clock frequency from interfering with the communication frequency of the radio communication in the electronic device disclosed in Japanese Unexamined Patent Application Publication No. 2010-141538 described above, suppressing the noises included in the output sounds by directly applying this technology to the FM receiver has the following problems:
First, the display unit of the FM receiver generally has a configuration using a fixed dot clock. It is necessary to make a significant change to the configuration in order to switch the dot clock frequency, and it is impractical to provide a mechanism to switch the frequency only for noise reduction. Since change of the resolution of the LCD in, for example, a notebook sized personal computer is assumed in the electronic device in Japanese Unexamined Patent Application Publication No. 2010-141538, a complicated mechanism to switch the dot clock frequency for the change of the resolution is provided in advance.
Second, in Japanese Unexamined Patent Application Publication No. 2010-141538, the dot clock frequency is switched when the notebook sized personal computer functions and the notebook sized personal computer is subsequently used with the switched dot clock frequency. Since the reception frequency is changed in response to an instruction from a user during the operation in the case of the FM receiver, switching the dot clock frequency each time the reception frequency is changed causes a flicker or the like in the display that possibly reduces the display quality.